Neurophysiology of the central nervous system

Dr. Loai AlzghoulLoai.physiology@yahoo.com

Organization of the nervous system

Organization of the nervous system

Levels of the CNS

1) Spinal cord2) Brain stem and sub cortical3) Cerebral cortex

3 Major Levels of CNS Function

• The spinal cord level.– more than just a conduit for signals from

periphery of body to brain and vice versa.– cord contains:

• walking circuits.• reflexes circuits.

The brain stem and subcortical

• Contains:– medulla, pons, mesencephalon,

hypothalamus, thalamus, cerebellum and basal ganglia.

• Controls subconscious body activities:– arterial pressure, respiration, equilibrium,

feeding reflexes, emotional patterns.

The Higher Brain or Cortical Level

• Higher order functions : language, thoughts and personality

• Large memory storehouse.• Each portion of the nervous system

performs specific functions, but it is the cortex that opens the world up for one’s mind.

Organization of the Nervous System

• Sensory Division– tactile, visual, auditory, olfactory.

• Motor Division– respond to and move about in our

environment.• Integrative Division

– process information, creation of memory.

Figure 45-2

SomatosensoryAxis of the Nervous System

Figure 45-3

Skeletal Motor Nerve Axis of the Nervous System

Terminology:

Afferent

VS

Efferent

Terminology:

1st order , 2nd order and 3rd order neurons

Histology of the NS

NeuronStructure

Types of neurons

Neuroglia

Neuroglia

Myelination

Neuroglia

Myelination

In PNS = Schwann cell

Neuroglia

Form the blood-cerebrospinal fluid barrier

Neuroglia

Neuroglia

Phagocytize

Neuroglia

Astrocytes

Astrocytes

Astrocytes

1) Support for neurons

2) Form the blood –brain barrier

3) Maintain the prober environment for the neurons

Nervous tissue

Nervous tissue

Gray matter : neuron cells White natter: myelinated axons

Synapses and Neurotransmitters

Communication Between Neurons

• Synapse:

Communication Between Neurons

• Synapse: A specialized site of contact, and transmission of information between a neuron and an effector cell

Figure 45-5

Anterior Motor Neuron

Communication Between Neurons

• Electrical synapse

Communication Between Neurons

• Electrical synapse Chemical synapse

Communication Between Neurons

• Chemical synapse

Neurotransmitter: is a messenger of

neurologic information from

one cell to another.

Synaptic Transmission

Action of Neurotransmitter on Postsynaptic Neuron

• postsynaptic membrane contains receptor proteins for the transmitter released from the presynaptic terminal.

• The effect of neurotransmitter on the post synaptic neuron depend on the type of the receptor

Action of Neurotransmitter on Postsynaptic Neuron

• Two types of receptors– Ion channels receptors

Action of Neurotransmitter on Postsynaptic Neuron

• Two types of receptors– Ion channels receptors– Second messenger receptors

Ion Channels receptors

• transmitters that open sodium channels excite the postsynaptic neuron.

• transmitters that open chloride channels inhibit the postsynaptic neuron.

• transmitters that open potassium channels inhibit the postsynaptic neuron.

Seconded messenger receptors(as example G-protein)

Ion Channel

1. Opening specific ion channels

2. Activation of cAMP or cGMP

3. Activation of one or more intracellular enzymes

4. Activation of gene transcription.